142 PALEONTOLOGY OF NEW YORK. 



The connected valves show a narrow ligamental area fxtemlini: liall' the 

 lono^th ol' the hini'c. Otlici' cliaiacters of tlie interior arc unknown. 



One specimen lias a length of 35 nun., height 21 mm., and hinge-line 25 

 mm. .\notlicr has a Icnirth of ^o mm., hcii;ht 1-'! mm., and liinge-line 2(1 mm. 



This species resend)les P. Kucrate, l)nt is less gibbous, more elongate, and 

 without angularity along the body. 



Formation and locality. In a conglomerate of the Chemung group at Panama, 

 Chautau(ina county, N. Y. 



Ptychopteri.v g.\lene, n. sp. 



I'l.ATK I. XXXV, KIOs 23-31. 



Shell small, rhondioidal : liody suli-dliptical. i)Mi(|ue at an angle of aliout 40° 

 with the hinge; height greatei' than half the length: ante-byssal margin 

 oblique, curving gently into a shallow siiuis ; base regularly rounded ; 

 posterior end al)ru])tly recur\ed. 



Left valve convex, moderately gibbous on the umbo, and sub-angular along 

 the upper half. Itight valve less convex above, depressed-convex in the 

 lower part. 



Ilinge-line straight, length greater than the height of the valvi". 



Beaks near the anterior third of tlie hinge, inclined forward, prominent, 

 arching over the hinge-line. Umbo gibbous, subtending somewhat less than 

 a right angle. 



Anterior end small, limited by the shallow, nearl\' Ncrtical byssal depres- 

 sion ; extremity acute. Wing wide-triangular, joining the bodx near 

 the posterior em! : limiting furrow distinct ; fold w ide and moderately 

 prominent; margin oliliiiiicly trinuati', \i'ry slightly concave just below the 

 hinge-line ; extremity angular. 



Surface ol' the body and wing marked by regular, line, interru|)ted or 

 undidating ladii. wliidi are olisciu'c or obsolete on the anti'rior ])ortion : also 

 In very line concentric lines, which are crowded into irregular fascicles and 

 are himellose on the anterior part of the valve. 



